Storage systems in which an information processing apparatus, such as a computer, and a storage apparatus are connected to a network are used. The network includes a relay apparatus which relays communication between nodes (such as an information processing apparatus and a storage apparatus). An information processing apparatus accesses a storage apparatus via a network. A network for a storage system may be referred to as a SAN (Storage Area Network). In a SAN Fibre Channel (FC), Ethernet (registered trademark), or the like is used as a network interface.
An information processing apparatus may be connected both to an FC network and to an Ethernet network. For example, an information processing apparatus may be connected to a SAN using FC and a SAN using Ethernet or be connected to a SAN using FC and a LAN (Local Area Network). In this case, the information processing apparatus may include both an FC adapter and an Ethernet adapter. However, if the information processing apparatus includes both an FC adapter and an Ethernet adapter, wiring may get complicated because wiring is performed according to adapters. Accordingly, the use of an adapter meeting Fibre Channel over Ethernet (FCoE) is proposed. The use of a single adapter meeting FCoE makes it possible to access both an FC network and an Ethernet network. As a result, wiring can be simplified.
With FCoE a unit of communication (FC frame) in FC is encapsulated in a unit of communication (Ethernet frame) in Ethernet. With FCoE enhanced Ethernet is used for performing communication by encapsulating an FC frame. The enhanced Ethernet may be referred to as DCB (Data Center Bridging). For example, a relay apparatus meeting FCoE includes both an FC port and an a DCB port. The relay apparatus extracts an FC frame from an Ethernet frame and transfers the FC frame from the FC port, or transfers an Ethernet frame from the DCB port.
A path along which a frame is transferred is selected in advance between relay apparatus by the use of, for example, a determined protocol and is held as transfer information by each relay apparatus. When a relay apparatus transfers a frame, it specifies on the basis of the transfer information a port where the frame is transferred. For example, when there is a change (blockage of a path or the like) in network, the transfer information is rewritten.
The following cross connect structure is proposed. When a plurality of communication paths can be used for relaying data, a faulty communication path of them is managed and control is exercised so as to stitch a data transfer path from the faulty communication path to a normal communication path.    Japanese Laid-open Patent Publication No. 2011-508523    Japanese Laid-open Patent Publication No. 2008-524936    Japanese Laid-open Patent Publication No. 2005-267599
As stated above, some relay apparatus can relay a first type of frame and a second type of frame which can include the first type of frame. With such relay apparatus transmitting a frame from a port specified on the basis of transfer information is not necessarily efficient. The reason for this is as follows. A load on the port may be heavy. Transmitting an additional frame from the port may increase the load on the port and a delay in communication may occur.
At this time there may be a path via a different type of port (DCB port for an FC port, for example) to a second relay apparatus to which an access destination node is connected. When a frame is transmitted to the second relay apparatus, usually a port determined by the transfer information is used. A load on the different type of port may be light. However, if the transfer information is not rewritten, the frame is transmitted from the same port that is determined by the transfer information. Accordingly, it is difficult to use the different type of port as a transfer destination port in place of the port determined by the transfer information.